In this bewildering world we have to decide what to believe and how to act on that. In principle that’s what science is for. “Science is not a body of facts,” says geophysicist Marcia McNutt, who once headed the U.S. Geological Survey and is now editor of Science, the prestigious journal. “Science is a method for deciding whether what we choose to believe has a basis in the laws of nature or not.” But that method doesn’t come naturally to most of us. And so we run into trouble, again and again.